The present invention relates to vehicle occupant protection systems or other safety systems employing pyrotechnic devices. One such pyrotechnic device may be a linear or pyrotechnic actuator to elevate a vehicle surface such as a hood, in the event of collision or impact with a pedestrian. Known linear or pyrotechnic actuators typically employ pyrotechnic means to activate a piston within an actuator. This increases the cost of manufacturing given that the gas generating composition must typically be contained, within a micro gas generator, for example. This therefore increases the complexity of the hood lifter or seat-belt pretensioner. Additionally, typical pyrotechnic compositions may increase the size of the actuator due to storage requirements within the actuator. It would therefore be an improvement to provide an alternative to the typical pyrotechnically actuated pistons. Furthermore, it would be an improvement in the art to combine the function of at least one or more structural features of the hood lifter/seat belt pretensioner, thereby simplifying the manufacture of the pyrotechnic actuator (e.g. hood lifter or seat belt pretensioner).